Kevin Porter's strained arch hurt so much that he wasn't sure he could play. But with center Wes Unseld already sidelined with a bad knee, Porter limped onto the floor, played in pain and dazzled the Chicago Bulls and a Capital Centre crowd of 17,682 yesterday, leading the Bullets to their most important victory this season.

Porter scored 28 points, 10 in the fourth quarter and six in a 90-second span late in the game that lifted the Bullets to a 103-99 victory. They moved within one game of the Bulls in the race for the sixth and final playoff spot in the Eastern Conference of the National Basketball Association.

The Bullets (35-37) ahve 10 games remaining, with seven of them at Capital Centre. Chicago (36-36) also has 10 games remaining, seven on the road. The Bulls won the season series with the Bullets, 5-1, and if they finish with identical records, the Bulls will make the playoffs.

"we've been winning all of the big games lately and this was the biggest one we had to win yet," said Coach Gene Shue as his team won for the fourth straight time. "The schedule is in our favor, so all we have to do is keep playing well and we should be okay."

Things looked bleak for the Bullets before the game. Unseld, who defends against 7-foot-2 Chicago center Artis Gilmore as well as anyone in t the Nba, showed up in such bad shape he couldn't even bend his right knee.

That knee forced Unseld to miss last Wednesday's game in San Diego, too. In that game, Shue started his small front line of Elvin Hayes at at center and Greg Ballard and Don Collins at forwards. He wasn't about to do that against the Bulls, the tallest team in the league with two 6-9 forwards and two 6-7 guards.

"there was no way I was going to start E on Gilmore because we couldn't afford to get him into foul trouble," said Shue.

So he started rookie Rick Mahorn at center.

Mahorn's statistics weren't impressive (three points and four rebounds), but his presence kept Hayes out of foul trouble and the Bullets were able to offset their height disadvantages.

Porter, the smallest man of the court, made the difference. Reggie Theus put Chicago on top, 95-93, with a three-point play with 2:30 to play. Thirty seconds later, Porter darted down the middle around Ricky Sobers for a layup that tied the score at 95.

Gilmore was called for an offensive foul on Chicago's next possession and Porter scored again. He penetrated down the middle, then lofted a running one-hander over Gilmore and David Greenwood.

Sobers missed for Chicago and Mitch Kupchak got the rebound (his 16th of the game) and started a fast break. Kevin Grevey converted if after an assist from Porter and the Bullets were ahead, 99-95, with 1:13 remaining.

Theus made a baseline jumper, but Porter got the lead back to four with a spectacular basket. Theus left Grevey to double-team Porter near the foul line. With Sober and Theus all over him, Porter pivoted, twirled the ball between his legs, faked a pass and then stepped into the lane between the two defenders and put in an eight-footer.

"I was trying to run a pick and roll with Mitch," Porter said, "but it wasn't there. I was trapped, but sometimes when you go between your legs it throws the defense off a bit."

Chicago still had a chance to win as Greenwood cut the lead to two points on a layup with 35 seconds left. The Bulls got the ball back with 18 seconds to play when Kupchak was called for traveling.

Chicago ran a play for Theus, but as he drove down the lane, Bob Dandridge stepped in front of him, causing him to bobble the ball and throw up an uncontrolled shot that bounced high off the glass. The rebound went out of bounds off Theus with five seconds to play.

The Bulls were then forced to foul to try to get the ball back; Theus fouled Grevey in the back court and Grevey made both free throws for the margin of victory.

Grevey and Hayes each finished with 18 points for the Bullets. Gilmore's 23 led Chicago.

The Bullets are off until Wednesday when they will face the New Jersey Nets in Piscataway and Unseld's status for that game is uncertain. "I don't know when or even if I can play," Unseld said.

Porter, who was limping again after the game, said he would be ready.

"He's such a fierce competitor it's amazing," said Grevey of his guard mate. "Sobers tried to intimidate him and it didn't work. He just wouldn't back down. He doesn't back down from anyone. He knows he's going to get clobbered on those drives he makes, but he still makes them. He's so confident that he can do anything on the floor he wants to and get away with it.

"When the games starts, he's just a mean little sucker and I'm awful glad we're on the same team